Sonoa gets drunk and ends up living at Tachibanakan. Yuu gets everyone to have a welcome party for Sonoa, so they meet by the riverside in appropriate outfits. Yuu has water guns waiting for them, and has everyone enter a "Water Gun Survival Game".
My pool time with Hanabi-oneechan...
Meine Poolzeit mit Hanabi-oneechan …
¿Y la hermanita Hanabi en la piscina?
¿Y la hermanita Hanabi en la piscina?
Adieu la piscine avec Hanabi…
Il mio momento di relax 
in piscina con la sorellona...
Minha piscina com a Hanabi-oneechan...